1. Field of the Invention
The present invention relates to a reflective (catoptric) imaging optical system, an exposure apparatus, and a method for producing a device. More specifically, the present invention relates to a reflective imaging optical system suitable for an exposure apparatus which uses, for example, the EUV light (EUV light beam) and transfers, onto a photosensitive substrate, a circuit pattern on a mask in accordance with the mirror projection method.
2. Description of the Related Art
Attention is directed to an EUVL (Extreme UltraViolet Lithography) exposure apparatus which uses the EUV (Extreme UltraViolet) light having a wavelength of, for example, about 5 nm to 40 nm as an exposure apparatus to be used for producing semiconductor elements, etc. In a case that the EUV light is used as the exposure light (exposure light beam), any usable transmissive optical material and any useable dioptric optical material are absent. Therefore, a reflection type mask is used, and a reflective optical system (optical system constructed of only reflecting members) is used as a projection optical system.
Conventionally, it has been suggested that a reflective optical system, which has an entrance pupil disposed on a side opposite to the optical system with an object plane intervening therebetween (an entrance pupil disposed on a side opposite to the optical system with respect to an object plane), is used as a reflective imaging optical system applicable to a projection optical system of an EUV exposure apparatus, in place of a reflective optical system which has an entrance pupil disposed on a side of the optical system with respect to an object plane (see, for example, U.S. Pat. No. 6,781,671). In the following description of this specification, the “reflective imaging optical system having the entrance pupil disposed on the side of the optical system with respect to the object plane” is referred to as “reflective imaging optical system of the near pupil type”, and the “reflective imaging optical system having the entrance pupil disposed on the side opposite to the optical system with respect to the object plane” is referred to as “reflective imaging optical system of the far pupil type”. The former is also referred to as “reflective imaging optical system of the normal pupil type” and the latter is also referred to as “reflective imaging optical system of the opposite pupil type”.